A new standard workflow to perform integrated interpretation of borehole images together with the other open hole logs was recently proposed (Chitale and Sullivan, 2004. Image logs provide high-resolution information on the layering, texture, and dip of rocks and sediments and permit core-like description of subsurface reservoirs. Conventional open hole wireline logs e.g., gamma, SP, resistivity, and porosity measured by nuclear, sonic, and NMR sensors provide complementary bulk petrophysical properties of formations. Thus, a proper integration of the electrical images with the conventional logs can provide an extremely powerful tool for reservoir characterization. The objective of standardizing the interpretation workflow is to de-mystify the image logs ? show that the borehole images are more than pretty pictures ? and increase their utilization in solving E&P problems.
This paper demonstrates that the borehole image log can be a powerful reservoir characterization tool available to an E&P asset team. It shows the implementation of the new image interpretation workflow in the case of a clastic- and a carbonate reservoir, respectively. The workflow involves integrating high resolution images with conventional open hole logs to identify lithofacies, depositional facies, and high frequency stratigraphic changes on the high resolution images. Sedimentary cycles and bed-sets and packages are then interpreted and combined with the other logs to generate electro-facies. Standard interpretation includes net-to-gross pay estimation. The above interpretation is then combined with the other well and field data to perform sequence stratigraphic analysis.
The paper includes case histories of successful applications from the Permian and the Fort Worth Basins.
Standardization of the borehole image interpretation helps reservoir characterization in the asset team environment. The standard workflow implementation requires the geologist, the petrophysicist and the reservoir engineer to work together closely so as to extract maximum value out of the image logs in terms of reservoir characterization. Benefits to the oil and gas operators include (1 enhanced accuracy in reserves estimation and reservoir fluid flow modeling; (2 more effective communication within and between various asset teams engaged in reservoir characterization; and (3 optimum utilization of the acquired down-hole data. All of the above directly save the E&P costs.